Refactor Message Pipeline And Observer Runtime

[Dumdart]

Summary

Refactors the message pipeline and observer runtime to clarify state ownership, persistence, hydration, and topic message handling across the application, GUI, and MCP layers.

Changes

Bug Fixes

• Improve observer model hydration, workspace persistence, broker snapshots, and topic message retention behavior.
• Align runtime and API state reporting with the updated observation model.

Features

• Add clearer interfaces and models for current topics, observation status, observer metadata, workspaces, and recorded messages.
• Improve broker profile and snapshot service integration.

Refactoring

• Separate message recording, topic reading, observer repository, and broker runtime responsibilities.
• Update dependency wiring, MQTT repositories, processors, GUI readers, MCP APIs, and database mappers to use the revised pipeline.

Improvements

• Update desktop workflow documentation and README guidance.
• Expand regression coverage across application, repository, runtime, GUI, MCP, hydration, retention, and presentation behavior.

Testing

• Added and updated unit and integration tests covering the refactored message pipeline, observer runtime, persistence, APIs, GUI state, hydration, and retention behavior.